Transmission

ABSTRACT

An oil pan includes a lubricant guide surface positioned above a lower end of an output gear located at the lowest position in a gear train. The lubricant guide surface is inclined so as to descend toward the output gear in an axial view of the output gear, and is inclined so as to descend from opposite ends to a central part in the axial direction of the output gear on the lubricant guide surface.

TECHNICAL FIELD

The present invention relates to a transmission.

BACKGROUND ART

There is hitherto known a transmission (speed reducer) that reduces a speed of an output of a driving source such as an electric motor via a plurality of gear trains.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Patent Laid-Open No. 2013-224710

SUMMARY OF INVENTION Technical Problem

In such a transmission as the above conventional one, it is common that a case supporting the gear train is filled with lubricant such as grease, but when the flowability of the lubricant is low, the supply of the lubricant by spraying of the lubricant cannot be expected, making it difficult to appropriately supply the lubricant to the entire gear train.

The present invention was made in view of the circumstances described above, and an object of the present invention is to make it possible to appropriately supply lubricant to an entire gear train in a transmission that transmits power of a driving source.

Solution to Problem

This specification includes all contents of Japanese Patent Application No. 2016-229332 filed on Nov. 25, 2016.

For achieving the above object, in one aspect of the present invention, in a transmission including: a gear train driven by a driving source; a case that supports the gear train inside; lubricant with which the case is filled; and an oil pan provided at a bottom of the case, the oil pan includes a lubricant guide surface positioned above a lower end of a lowermost-level gear that is positioned at the lowest position in the gear train, and the lubricant guide surface is inclined so as to descend toward the lowermost-level gear in an axial view of the lowermost-level gear, and is inclined so as to descend from opposite ends to a central part in the axial direction of the lowermost-level gear on the lubricant guide surface.

With the configuration according to the one aspect of the present invention, the oil pan includes the lubricant guide surface positioned above the lower end of the lowermost-level gear, and the lubricant guide surface is inclined so as to descend toward the lowermost-level gear in the axial view of the lowermost-level gear, and is inclined so as to descend from opposite ends to the central part in the axial direction of the lowermost-level gear on the lubricant guide surface. Accordingly, by the lubricant guide surface that is inclined so as to descend toward the lowermost-level gear in the axial view of the lowermost-level gear and is inclined so as to descend from opposite ends toward the central part, the lubricant guided to the oil pan can be guided to the bottom of the oil pan in the vicinity of the lowermost-level gear. Hence the lubricant circulating in the case can be once collected to the vicinity of the lowermost-level gear and efficiently circulated throughout the gear train from the lowermost-level gear side, whereby the lubricant can be appropriately supplied to the entire gear train.

In one aspect of the present invention, the case includes a side wall facing a tip of a driving source output shaft of the driving source, and the side wall includes an inclined portion that is inclined so as to be more separated in the axial direction from the driving source output shaft toward the oil pan on a lower side.

With the configuration according to the one aspect of the present invention, it is possible to efficiently guide the lubricant in the case to the oil pan on the lower side along the inclined portion of the side wall.

Further, in one aspect of the present invention, the gear train includes a counter gear that meshes with the driving source output shaft, and the lowermost-level gear that meshes with the counter gear, the counter gear integrally includes a driven gear portion that meshes with the driving source output shaft, and a driving gear portion that meshes with the lowermost-level gear, and at least a part of the driven gear portion is positioned inside the oil pan.

With the configuration according to one aspect of the present invention, the counter gear integrally includes a driven gear portion that meshes with the driving source output shaft, and a driving gear portion that meshes with the lowermost-level gear, and at least a part of the driven gear portion is positioned inside the oil pan. Hence the lubricant can be supplied to the driving source output shaft by the driven gear portion, a part of which is positioned inside the oil pan to mesh with the driving source output shaft. Further, the lubricant can be supplied to the driving gear portion by the lowermost-level gear that meshes with the driving gear portion.

Further, in one aspect of the present invention, a guide rib protruding to an inside of the case is formed in the inclined portion, and the guide rib extends in an up-down direction.

With the configuration according to the one aspect of the present invention, since the guide rib formed in the inclined portion extends in the up-down direction, it is possible to efficiently guide the lubricant to the oil pan on the lower side along the guide rib.

In one aspect of the present invention, the driving gear portion has a diameter smaller than that of the driven gear portion and is provided closer to the side wall side than the driven gear portion.

With the configuration according to one aspect of the present invention, the guide rib can be compactly provided effectively using the space on the driving gear portion having a diameter smaller than that of the driven gear portion.

Further, in one aspect of the present invention, the guide rib is provided above the driving gear portion, and overlaps with at least one of the driven gear portion and a gear of the driving source output shaft in the axial view of the counter gear.

With the configuration according to one aspect of the present invention, the guide rib is provided above the driving gear portion, and overlaps with at least one of the driven gear portion and a gear of the driving source output shaft in the axial view of the counter gear. Hence the guide rib can be compactly provided by effectively using the space above the driving gear portion having a diameter smaller than that of the driven gear portion. In addition, the lubricant from the driven gear portion and the gear of the driving source output shaft can be efficiently guided by the guide rib.

In one aspect of the present invention, the oil pan includes a lower end storage that is depressed downward along the lower end of the lowermost-level gear to constitute a lower end of the oil pan.

With the configuration according to one aspect of the present invention, the lubricant can be collected to the lower end storage and effectively circulated, and the oil pan can be compactly formed in the peripheral portion of the lower end storage.

Further, in one aspect of the present invention, the lubricant guide surface is inclined so as to descend toward the lower end storage.

With the configuration according to one aspect of the present invention, the lubricant guide surface is inclined so as to descend toward the lower end storage. With the lower end storage being the lower end of the oil pan, the lubricant can be easily collected and the lubricant can be efficiently supplied from the lower end storage to the gear train.

Further, in one aspect of the present invention, the lubricant guide surface is provided below the inclined portion.

With the configuration according to one aspect of the present invention, since the lubricant guide surface is provided below the inclined portion, the lubricant guided downward from the inclined portion can be efficiently guided to the lowermost-level gear side by the lubricant guide surface.

Advantageous Effects of Invention

In the transmission according to one aspect of the present invention, it is possible to appropriately supply lubricant to an entire gear train.

It is also possible to efficiently guide the lubricant to the oil pan on the lower side along the inclined portion of the side wall.

It is also possible to appropriately supply the lubricant to the driving source output shaft and the driving gear portion.

It is also possible to efficiently guide the lubricant to the oil pan on the lower side along the guide rib.

It is also possible to compactly provide the guide rib.

It is also possible to efficiently supply the lubricant from the lower end storage of the oil pan to the gear train, and compactly form the oil pan.

It is also possible to efficiently guide the lubricant guided downward from the inclined portion to the lowermost-level gear side with the lubricant guide surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a left side view of a lawn mower according to an embodiment of the present invention.

FIG. 2 is a left side view of the rear of the lawn mower.

FIG. 3 is a perspective view of a transmission as viewed from the left front side.

FIG. 4 is a left side view of the transmission.

FIG. 5 is a sectional view taken along a line V-V of FIG. 4.

FIG. 6 is a sectional view taken along a line VI-VI of FIG. 4.

FIG. 7 is a sectional view of an oil pan taken along a plane vertical to an axial direction of a counter gear.

DESCRIPTION OF EMBODIMENT

Hereinafter, the embodiment of the present invention will be described with reference to the drawings. During the description, directions such as front-rear, right-left, and up-down will be described taking a forward direction of a lawn mower 1 (work machine) as the front of the machine body. Symbol FR indicated in each drawing denotes the front of the machine body, symbol UP denotes the upper part of the machine body, and symbol LH denotes the left of the machine body.

FIG. 1 is a left side view of the lawn mower 1 according to the embodiment of the present invention. FIG. 2 is a left side view of the rear of the lawn mower 1. In FIGS. 1 and 2, as for ones provided as a lateral pair, only the left-side one is illustrated including its numeral. In addition, in FIG. 2, a part of the machine body is omitted for illustrating the internal configuration of the rear of the lawn mower 1.

The lawn mower 1 is a walking type self-propelled work machine with which an operator walks while operating the self-propelled lawn mower 1.

The lawn mower 1 includes: a housing 10; a lateral pair of front wheels 11, 11 provided on the right and left of the front of the housing 10; a lateral pair of rear wheels 12, 12 provided on the right and left of the rear of the housing 10; a lawn mowing cutter blade 13 housed inside the housing 10; and a driving motor (not illustrated) as a power source to drive the cutter blade 13. The driving motor is supported by the housing 10. Note that the power source of the cutter blade 13 may be an engine.

Further, the lawn mower 1 includes; an electric motor 14 (driving source) as a travelling power source to drive the rear wheels 12, 12; a transmission 15 that transmits the power of the electric motor 14 to each of the rear wheels 12, 12; a box-shaped mown grass container 16 attached to the rear of the housing 10; an operation handle 17 extending rearward and upward from the rear of the housing 10. The upper end of the operation handle 17 is provided with an operation unit 17 a for the operator to control the number of revolutions of the driving motor, the number of revolutions of the electric motor 14, and the like. The transmission 15 is provided in the rear of the housing 10.

The electric motor 14 is driven by a battery mounted in the lawn mower 1. The lawn mower 1 moves forward by rotation of the rear wheels 12, 12 that are driven by the electric motor 14. As the driving source, an engine (internal combustion engine) may be used in place of the electric motor 14.

The housing 10 is formed in the shape of a case with its lower surface open, the lower surface facing a lawn, and the cutter blade 13 faces the lawn from the open portion on the lower surface of the housing 10. The cutter blade 13 is fixed to the lower end of a rotation shaft 18 extending in the up-down direction inside the housing 10, and mows glass by rotating around the rotation shaft 18 driven by the driving motor. The glass mown with the cutter blade 13 is called “mown glass.” The mown glass is discharged rearward through a path in the housing 10 and housed into the mown grass container 16.

FIG. 3 is a perspective view of the transmission 15 as viewed from the left front side. FIG. 4 is a left side view of the transmission 15. FIG. 5 is a sectional view taken along a line V-V of FIG. 4.

With reference to FIGS. 3 to 5, the transmission 15 includes: an input shaft 20 into which the power from the electric motor 14 is input; a transmission shaft 21 that meshes with the input shaft 20; and an output shaft 22 that meshes with the transmission shaft 21. The input shaft 20, the transmission shaft 21, and the output shaft 22 extend parallel to one another in a machine-width direction of the lawn mower 1.

Further, the transmission 15 includes an input shaft 20, a case 23 that houses the transmission shaft 21 and the output shaft 22; an adapter 24 interposed between the case 23 and the electric motor 14, and a cover member 25 that covers the electric motor 14.

The transmission 15 is a speed reducer that reduces the speed of rotation, input from the electric motor 14, and outputs the rotation from the output shaft 22.

The electric motor 14 includes a cylindrical motor body portion 14 a having a rotor and the like provided inside, and a motor output shaft 14 b (driving source output shaft) extending from the central part of the motor body portion 14 a.

The input shaft 20 includes a motor output shaft 14 b, and an input gear 26 (a gear of the driving source output shaft) fixed to the motor output shaft 14 b.

The transmission shaft 21 includes a shaft 27 supported by the case 23, and a counter gear 28 (gear) that meshes with the input gear 26 and is rotatable on the shaft 27.

The output shaft 22 includes an axle 29 supported by the case 23, and an output gear 30 (lowermost-level gear) that meshes with the counter gear 28 of the transmission shaft 21 and is integrally fixed with the axle 29.

The axle 29 is provided penetrating the case 23 of the lawn mower 1 in the machine-width direction. That is, the transmission 15 is mounted in the lawn mower 1 with the axle 29 extending in the machine-width direction. The right and left rear wheels 12, 12 (FIG. 1) are respectively provided at the right and left ends of the axle 29. Specifically, the transmission 15 is disposed to be offset on one side (left side) with respect to the center of the machine width of the lawn mower 1. Hence an amount of the axle 29 extended from the transmission 15 is smaller on the left side than on the right side.

The electric motor 14 is fixed to the right side surface of the case 23 via the adapter 24. In other words, the electric motor 14 is fixed to the inner side surface of the case 23 in the machine-width direction.

The case 23 includes, a case body 31 that houses a gear train 19 made up of the input gear 26, the counter gear 28, and the output gear 30, and an oil pan 32 provided at the bottom of the case body 31.

The case body 31 includes a one-side side wall 33 through which the motor output shaft 14 b of the electric motor 14 is inserted from the outside, the other-side side wall 34 (side wall) facing the one-side side wall 33, a wall 35 constituting the front surface, the upper surface, and the rear surface of the case body 31, and the lower-surface opening 36 that opens downward the internal space of the case body 31. The lower-surface opening 36 is blocked by the oil pan 32.

As illustrated in FIG. 5, an insertion hole 37, through which the one-side side wall 33 penetrates, is formed in the one-side side wall 33 in the upper part of the case body 31, and the motor output shaft 14 b constituting the input shaft 20 is inserted through the insertion hole 37 from the outside.

The transmission shaft 21 is supported by a shaft support portion 38 disposed immediately below the input shaft 20 and formed in the case body 31. The shaft support portion 38 includes a one-side support hole portion 39 (support hole portion) provided in the one-side side wall 33, and the other-side support hole portion 40 provided in the other-side side wall 34 in a concentric positional relation with the one-side support hole portion 39.

The one-side support hole portion 39 is a through hole penetrating the one-side side wall 33 in the machine-width direction, and is formed with an opening 39 a that communicates the space in the case body 31 to the outside. The other-side support hole portion 40 is a blind hole formed in the inner surface of the other-side side wall 34, and does not penetrate the other-side side wall 34.

The shaft 27 of the transmission shaft 21 is fixed to the case body 31 by fitting of one end 27 a (one end of the transmission shaft and one end of the shaft) into the one-side support hole portion 39 and by fitting of the other end 27 b into the other-side support hole portion 40.

The one end 27 a of the shaft 27 is formed with a protrusion 27 c protruding from the opening 39 a of the one-side support hole portion 39 to the outside of the one-side side wall 33.

Further, a seal member 41 is provided between the outer periphery of the one end 27 a and the inner periphery of the one-side support hole portion 39. The seal member 41 is an O-ring made of rubber, for example, and fitted into an annular groove formed in the outer periphery of the one end 27 a.

The counter gear 28 of the transmission shaft 21 is rotatably provided on the shaft 27 by engagement of a hole portion, provided at the center of the counter gear 28, with the outer periphery of the portion between the one end 27 a and the other end 27 b of the shaft 27.

The counter gear 28 has a driven gear portion 28 a that meshes with the input gear 26, and a driving gear portion 28 b that meshes with the output gear 30. The driven gear portion 28 a and the driving gear portion 28 b are integrally formed while arranged in the axial direction of the shaft 27, the driven gear portion 28 a is positioned on the one-side side wall 33 side and the driving gear portion 28 b is positioned on the other-side side wall 34 side. The driving gear portion 28 b is a gear having a diameter smaller than that of the driven gear portion 28 a.

The output shaft 22 is disposed below the transmission shaft 21 and in a position offset in the front-rear direction (rear) with respect to the transmission shaft 21.

The case body 31 includes an axle support hole portion 43 penetrating the one-side side wall 33, and an axle support hole portion 44 provided concentrically with the axle support hole portion 43 and penetrating the other-side side wall 34.

The axle 29 of the output shaft 22 is inserted into the axle support hole portions 43, 44 to be pivotally supported by the axle support hole portion 43 and the axle support hole portion 44. Specifically, the axle 29 is supported via cylindrical bushes 45, 45 fitted to the inner peripheries of the axle support hole portions 43, 44. In addition, annular oil seals 46, 46, which seal between the axle 29 and the axle support hole portions 43, 44, are provided outside the bushes 45, 45 in the axial direction in the axle support hole portions 43, 44.

The output gear 30 is fixed to the axle 29 with a pin 47 that is provided so as to penetrate the output gear 30 and the axle 29 in a radial direction. The output gear 30 is a gear having a diameter larger than that of the driving gear portion 28 b of the counter gear 28.

FIG. 6 is a sectional view taken along a line VI-VI of FIG. 4.

With reference to FIGS. 4 to 6, the adapter 24 includes the platy portion 50 formed in a circular plate shape, a tubular portion 51 protruding in a plate thickness direction from the central part of the platy portion 50, a fixing portion 52 provided on the outer periphery of the platy portion 50, a cover fixing portion 53 to which the cover member 25 is fixed, and a motor fixing portion 54.

The platy portion 50 includes a case contact surface 50 a in contact with the outer surface of the one-side side wall 33 of the case body 31, and a motor attachment surface 50 b to which the motor body portion 14 a is attached on the rear surface side of the case contact surface 50 a. The case contact surface 50 a is formed with a contact portion 50 c (FIG. 5) in contact with the one end 27 a of the shaft 27.

The adapter 24 is made of a material having electric insulation and is made of resin, ceramics, or the like.

A fixing portion 52 is a hole for insertion of an adapter fixing bolt 55 that fixes the adapter 24 to the case body 31. A plurality of fixing portions 52 are provided at substantially equal intervals in a circumferential direction of the platy portion 50.

A plurality of cover fixing portions 53 are provided at substantially equal intervals in the circumferential direction of the platy portion 50.

The motor fixing portion 54 is a hole portion for fastening of a motor fixing bolt 56 (FIG. 6) that fastens the motor body portion 14 a to the adapter 24. A plurality of motor fixing portions 54 are provided at substantially equal intervals in the circumferential direction of the platy portion 50. Each of the motor fixing portions 54 is provided at a position more inside than the fixing portion 52 and the cover fixing portion 53 in the radial direction of the platy portion 50.

The adapter 24 is disposed such that the case contact surface 50 a comes into contact with the one-side side wall 33 while a tubular portion 51 is fitted into the insertion hole 37 of the one-side side wall 33, and the adapter 24 is fastened to one-side side wall 33 with the adapter fixing bolt 55 that is inserted into each fixing portion 52 from the motor attachment surface 50 b side.

The electric motor 14 is disposed such that the motor output shaft 14 b is inserted into the tubular portion 51 of the adapter 24 and the end surface of the motor body portion 14 a comes into contact with the motor attachment surface 50 b of the adapter 24. The electric motor 14 is fastened to the motor fixing portion 54 with a motor fixing bolt 56 that is inserted through a flange portion 14 c on the outer periphery of the motor body portion 14 a.

As thus described, by attaching the electric motor 14 to the insulating adapter 24, the electric motor 14 can be fixed to the transmission 15 while being electrically insulated from the case 23.

As illustrated in FIG. 5, in the state where the adapter 24 has been attached to the case body 31, the contact portion 50 c of the adapter 24 comes into contact with the protrusion 27 c of the one end 27 a of the shaft 27 protruding to the outside through the opening 39 a, and presses the shaft 27 to the other-side support hole portion 40 side in the axial direction. That is, the shaft 27 of the transmission shaft 21 is retained with respect to the shaft support portion 38 by the contact portion 50 c of the adapter 24.

Specifically, the contact portion 50 c is a recess formed by recessing of the case contact surface 50 a in the protruding direction of the protrusion 27 c, and the protrusion 27 c comes into contact with the bottom of the recess.

As thus described, the shaft 27 can be retained by the adapter 24 configured to fix the electric motor 14 in the insulated state to the transmission 15, so that it is possible to omit a dedicated retaining member and simplify the structure of the transmission 15.

With the one-side support hole portion 39 including the opening 39 a, one end 27 a of the shaft 27 and the contact portion 50 c can be easily brought into contact with each other through the opening 39 a.

Further, in the transmission shaft 21, the counter gear 28 rotates on the shaft 27 and the shaft 27 hardly rotates, so that the shaft 27 can be retained even in the configuration where the adapter 24 is brought into contact with the one end 27 a of the shaft 27.

Moreover, with the seal member 41 provided between the one end 27 a of the shaft 27 and the one-side support hole portion 39, the sealability of the case body 31 can be ensured even in the configuration where the one-side support hole portion 39 includes the opening 39 a.

The cover member 25 integrally includes a tubular peripheral wall 25 a that covers the outer periphery of the motor body portion 14 a, and a side wall 25 b that closes one end of the peripheral wall 25 a to cover the end surface of the motor body portion 14 a in the axial direction. In the peripheral wall 25 a and the side wall 25 b, a plurality of air vents 25 c are formed.

The peripheral wall 25 a includes an engagement piece 25 d protruding to the adapter 24 side from the end opposite from the side wall 25 b. The engagement piece 25 d includes a protrusion 25 e protruding from the outer periphery of the tip to the outside of the peripheral wall 25 a in the radial direction in a fingernail shape. A plurality of engagement pieces 25 d are formed at substantially equal intervals in the circumferential direction of the peripheral wall 25 a.

The cover fixing portion 53 of the adapter 24 is a hole portion into which the engagement piece 25 d of the cover member 25 is inserted. The cover member 25 is fixed to the adapter 24 by insertion and engagement of each engagement piece 25 d into each cover fixing portion 53.

The case 23 is filled with lubricant (not illustrated) that makes the input shaft 20, the transmission shaft 21, and the output shaft 22 lubricant. The lubricant is grease in the present embodiment, but the lubricant may be oil. The lubricant is stored in the lower part of the case 23 including the oil pan 32.

In the case 23, the input gear 26, the counter gear 28, and the output gear 30 are arranged sequentially from above in the up-down direction.

As illustrated in FIG. 4, the lower parts of the counter gear 28 and the output gear 30 are positioned inside the oil pan 32.

In the counter gear 28 and the output gear 30, at least the lower ends 28 c, 30 a are positioned inside the oil pan 32 and in contact with the lubricant stored in the oil pan 32. For this reason, in a state where the transmission 15 is driven by the electric motor 14, the lubricant of the oil pan 32, which adheres to each of the counter gear 28 and the output gear 30, is supplied upward by centrifugal force of the rotation of each of the counter gear 28 and the output gear 30, and is also supplied to a gear that directly meshes with the counter gear 28 and the output gear 30.

Specifically, as illustrated in FIG. 4, the output gear 30 meshes with the gear portion 28 b of the counter gear 28, thereby enabling adhesion of the lubricant of the oil pan 32 to the driving gear portion 28 b via the output gear 30. It is thus possible to appropriately supply the lubricant to the driving gear portion 28 b positioned above the oil pan 32.

Further, as illustrated in FIG. 4, the driven gear portion 28 a of the counter gear 28 has its lower end 28 c positioned inside the oil pan 32 and meshes with the input gear 26 of the electric motor 14. This enables adhesion of the lubricant of the oil pan 32 to the input gear 26 via the driven gear portion 28 a. It is thus possible to appropriately supply the lubricant to the input gear 26 positioned above the oil pan 32.

A part of the lubricant, supplied from the oil pan 32 to the input gear 26, the counter gear 28, and the output gear 30, drops by gravity to return to the oil pan 32 and is supplied again from the oil pan 32 to each of the input gear 26, the counter gear 28, and the output gear 30.

With reference to FIGS. 3 to 5, the other-side side wall 34 facing the tip of the motor output shaft 14 b includes in its upper part a perpendicular portion 34 a facing the tip of the motor output shaft 14 b, and an inclined portion 34 b inclined from the lower end of the perpendicular portion 34 a and extending downward.

The inclined portion 34 b is inclined so as to be more separated in the axial direction from the motor output shaft 14 b toward the lower oil pan 32 side. The inclined portion 34 b is provided immediately above the gear portion 28 b of the counter gear 28, and formed in a position overlapping with the side surface of the upper part of the driven gear portion 28 a in the axial view of the driven gear portion 28 a as illustrated in FIG. 4. The interval between the inclined portion 34 b and the side surface of the driven gear portion 28 a increases in the downward direction.

The inclined portion 34 b includes, on its inner surface, guide ribs 60, 60 protruding to the inside of the case 23. A pair of guide ribs 60, 60 are provided substantially parallel to an imaginary line S connecting the center of the input gear 26 and the center of the counter gear 28, and extend in the up-down direction. As illustrated in FIG. 4, the pair of guide ribs 60, 60 are provided so as sandwich the line S from opposite sides in the axial view of the counter gear 28, and are arranged in the front and rear of the counter gear 28.

The guide ribs 60, 60 are provided below the input gear 26 and above the driving gear portion 28 b, and are formed in positions overlapping with the side surface of the upper part of the driven gear portion 28 a in the axial view of the counter gear 28 (FIG. 4).

FIG. 7 is a sectional view of the oil pan 32 taken along a plane vertical to the axial direction of the counter gear 28. In FIG. 7, the gear train 19 is illustrated together with the oil pan 32.

With reference to FIGS. 3 to 5, and 7, the oil pan 32 includes a pot-like storage 61 with its upper surface open, and a flange portion 62 extending from the upper edge of the storage 61 to the lateral outside. The oil pan 32 is fixed to the lower surface of the case body 31 with a plurality of oil pan fixing bolts 63 inserted into the flange portion 62 from below.

The storage 61 includes a lower end storage 65 and a lubricant introduction portion 66 formed above the lower end storage 65, the lower end storage 65 covering from below the output gear 30 that is the lowermost-level gear located at the lowest position in the gear train 19.

The lubricant introduction portion 66 is positioned immediately below the counter gear 28 and covers the counter gear 28 from below.

The lower end storage 65 constitutes the lower end of the oil pan 32 that is depressed downward along the lower end 30 a of the output gear 30.

The bottom of the lubricant introduction portion 66 is formed by a lubricant guide surface 67 that is inclined so as to descend toward the lower end storage 65.

Specifically, as illustrated in FIG. 7, in the axial view of the output gear 30, the lubricant guide surface 67 is inclined so as to descend toward the output gear 30 from an upper end 67 a, which is positioned on the opposite side from the lower end storage 65, to a lower end 67 b. Further, as illustrated in FIG. 5, the lubricant guide surface 67 is inclined so as to descend from opposite ends 67 c, 67 c of the output gear 30 in the axial direction on the lubricant guide surface 67 toward a central part 67 d of the output gear 30 in the axial direction on the lubricant guide surface 67. A valley shape going downward from opposite ends 67 c, 67 c toward the central part 67 d is formed in the range from the upper end 67 a to the lower end 67 b. That is, the lubricant guide surface 67 is formed in a tub shape declining toward the output gear 30 and depressed such that the central part 67 d in the width direction is the lowest.

With reference to FIGS. 4 and 5, when a part of lubricant L, supplied from the oil pan 32 to each of the input gear 26 and the counter gear 28, drops and returns to the oil pan 32 as illustrated in FIGS. 4 and 5, the part of the lubricant L moves downward along the inner surface of the inclined portion 34 b positioned below the input gear 26. In the present embodiment, since the internal space of the case 23 is wider on the lower side due to the inclined portion 34 b, it is possible to efficiently guide the lubricant in the upper part of the case 23 to the oil pan 32 on the lower side.

Further, since the guide ribs 60, 60 extending in the up-down direction are formed in the inclined portion 34 b, the rigidity of the other-side side wall 34 can be improved by the guide ribs 60, 60, and the lubricant can be efficiently guided by the guide ribs 60, 60 to the oil pan 32 on the lower side

The lubricant having moved from the inclined portion 34 b to the lubricant guide surface 67 immediately below the inclined portion 34 b moves downward to the output gear 30 side along the lubricant guide surface 67 that declines toward the lower end storage 65, and reaches the lower end storage 65. In the present embodiment, the lubricant guide surface 67 is inclined so as to descend from opposite ends 67 c, 67 c of the output gear 30 in the axial direction on the lubricant guide surface 67 toward the central part 67 d, whereby the lubricant can be collected to the central part 67 d and the flow of the lubricant moving downward toward the lower end storage 65 can be formed easily. It is thereby possible to efficiently return the lubricant to the lower end storage 65 and efficiently circulate the lubricant from the lower end storage 65 to the gear train 19.

As described above, according to the embodiment to which the present invention has been applied, the transmission 15 includes: the transmission shaft 21 driven by the electric motor 14; and the case 23 that supports the electric motor 14 and the transmission shaft 21, the transmission including the adapter 24 which is interposed between the case 23 and the electric motor 14 and to which the electric motor 14 is attached, and the adapter 24 is in contact with one end 27 a of the transmission shaft 21 in the axial direction of the transmission shaft 21. As a result, the transmission shaft 21 can be retained using the adapter 24 to which the electric motor 14 is attached, so that it is possible to omit a dedicated retaining member and simplify the structure of the transmission 15.

Further, since the adapter 24 is made of a material having electric insulation, it is possible to attach the electric motor 14 to the transmission 15 in an electrically insulated state, and retain the transmission shaft 21 by using the adapter 24.

Moreover, the case 23 includes the opening 39 a that exposes the one end 27 a of the transmission shaft 21 to the outside of the case 23, and the one end 27 a of the transmission shaft 21 and the adapter 24 are in contact with each other in the axial direction of the transmission shaft 21 through the opening 39 a. It is thus possible to bring the adapter 24 into contact with the one end 27 a of the transmission shaft 21 exposed from the opening 39 a and retain the transmission shaft 21 with a simple structure.

The transmission shaft 21 includes the shaft 27 supported by the case 23, and the counter gear 28 rotationally provided on the shaft 27 to mesh with the motor output shaft 14 b of the electric motor 14, and the shaft 27 is retained by the adapter 24. As a result, the shaft 27 supporting the counter gear 28 hardly rotates, so that the shaft 27 can be easily retained by the adapter 24.

Further, the case 23 includes the one-side support hole portion 39 that supports the one end 27 a of the shaft 27 and communicates with the inside and the outside of the case 23, the one end 27 a and the adapter 24 are in contact with each other in the axial direction of the shaft 27 through the support hole portion 39, and the seal member 41 is provided between the outer periphery of the one end 27 a and the support hole portion 39. Hence the one end 27 a of the shaft 27 and the adapter 24 can be brought into contact with each other through the one-side support hole portion 39 of the case 23 to retain the shaft 27 with a simple structure, and the case 23 can be favorably sealed by the seal member 41 provided between the outer periphery of the one end 27 a and the support hole portion 39.

Moreover, since the cover member 25 covering the electric motor 14 is attached to the adapter 24, it is possible to attach the cover member 25 with a simple structure.

According to the embodiment to which the present invention has been applied, the transmission 15 includes: the gear train 19 driven by the electric motor 14; the case 23 that supports the gear train 19 inside; the lubricant that fills the case 23; and the oil pan 32 provided at the bottom of the case 23, the oil pan 32 includes the lubricant guide surface 67 that is positioned above the lower end 30 a of the output gear 30 located at the lowest position in the gear train 19, and the lubricant guide surface 67 is inclined so as to descend toward the output gear 30 in the axial view of the output gear 30, and is inclined so as to descend from opposite ends 67 c, 67 c of the output gear 30 in the axial direction on the lubricant guide surface 67 toward the central part 67 d. Accordingly, by the lubricant guide surface 67 that is inclined so as to descend toward the output gear 30 in the axial view of the output gear 30 and is inclined so as to descend from opposite ends 67 c, 67 c toward the central part 67 d, the lubricant guided to the oil pan 32 can be guided to the bottom of the oil pan 32 in the vicinity of the output gear 30. Hence the lubricant circulating in the case 23 can be once collected to the vicinity of the output gear 30 and efficiently circulated throughout the gear train 19 from the output gear 30 side, and the lubricant can be appropriately supplied to the entire gear train 19.

The case 23 includes the other-side side wall 34 facing the tip of the motor output shaft 14 b of the electric motor 14, and the other-side side wall 34 includes the inclined portion 34 b that is inclined so as to be more separated from the motor output shaft 14 b in the axial direction toward the lower oil pan 32 side. Accordingly, it is possible to efficiently guide the lubricant in the case 23 to the oil pan 32 on the lower side along the inclined portion 34 b of the other-side side wall 34.

The gear train 19 includes the counter gear 28 that meshes with the motor output shaft 14 b and the output gear 30 that meshes with the counter gear 28, the counter gear 28 integrally includes the driven gear portion 28 a that meshes with the motor output shaft 14 b and the driving gear portion 28 b that meshes with the output gear 30, and in the driven gear portion 28 a, at least the lower end 28 c is positioned inside the oil pan 32. Hence the lubricant can be supplied to the motor output shaft 14 b by the driven gear portion 28 a that has its lower end 28 c positioned inside the oil pan 32 and meshes with the motor output shaft 14 b. Further, the lubricant can be supplied to the driving gear portion 28 b by the output gear 30 that meshes with the driving gear portion 28 b provided inside the oil pan 32.

The guide ribs 60, 60 protruding to the inside of the case 23 are formed in the inclined portion 34 b, and the guide ribs 60, 60 are extended in the up-down direction, whereby it is possible to efficiently guide the lubricant to the oil pan 32 on the lower side along the guide ribs 60, 60.

The driving gear portion 28 b has a diameter smaller than that of the driven gear portion 28 a and is provided closer to the other-side side wall 34 side than the driven gear portion 28 a. Hence the guide ribs 60, 60 can be compactly provided effectively using the space on the driving gear portion 28 b having a diameter smaller than that of the driven gear portion 28 a.

The guide ribs 60, 60 are provided above the driving gear portion 28 b, and overlap with the driven gear portion 28 a in the axial view of the counter gear 28. Hence the guide ribs 60, 60 can be compactly provided effectively using the space above the driving gear portion 28 b having a diameter smaller than that of the driven gear portion 28 a. Further, the lubricant from the driven gear portion 28 a can be efficiently guided by the guide ribs 60, 60.

The oil pan 32 includes the lower end storage 65 constituting the lower end of the oil pan 32 that is depressed downward along the lower end 30 a of the output gear 30. Accordingly, the lubricant can be collected to the lower end storage 65 and effectively circulated, and the oil pan 32 can be compactly formed in the peripheral portion of the lower end storage 65.

The lubricant guide surface 67 is inclined so as to descend toward the lower end storage 65. With the lower end storage 65 being the lower end of the oil pan 32, the lubricant can be easily collected and the lubricant can be efficiently supplied from the lower end storage 65 to the gear train 19.

Further, with the lubricant guide surface 67 being provided below the inclined portion 34 b, the lubricant guided downward from the inclined portion 34 b can be efficiently guided to the lowermost-level gear side by the lubricant guide surface 67.

Note that the above embodiment illustrates one aspect to which the present invention has been applied, but the present invention is not limited to the above embodiment.

In the above embodiment, the description has been given assuming that the contact portion 50 c that is the recessed portion of the adapter 24 comes into contact with the one end 27 a of the shaft 27 protruding outside through the opening 39 a, but the present invention is not limited thereto, and the contact portion 50 c may only have a shape capable of retaining the shaft 27. For example, the one end 27 a of the shaft 27 may be formed to be flush with the outer end of the opening 39 a and the flat contact portion of the adapter 24 may be brought into contact with the one end 27 a. Alternatively, in order for the one end 27 a to be positioned more inside than the outer end of the opening 39 a, the shaft 27 may be formed shorter than the state of FIG. 5, a protruding contact portion that protrudes to the inside of the opening 39 a may be formed in the adapter 24, and the contact portion may be brought into contact with the one end 27 a. The contact portion 50 c may not necessarily be in constant contact with the one end 27 a, but may be configured to come into contact with the one end 27 a at the time of movement of the shaft 27.

Further, the contact portion 50 c may come into contact with the shaft 27 via the spacer that is interposed between the contact portion 50 c and the one end 27 a.

In the above embodiment, the description has been given assuming that the contact portion 50 c that is the recessed portion of the adapter 24 comes into contact with the one end 27 a of the shaft 27, but a gap may be formed between the one end 27 a and the contact portion 50 c as long as the shaft 27 can be retained by the adapter 24. In this instance, by shifting the shaft 27 to the contact portion 50 c side in the axial direction, the one end 27 a comes into contact with the contact portion 50 c, and the shaft 27 is retained.

In the above embodiment, the description has been given assuming that the guide ribs 60, 60 overlap with the driven gear portion 28 a in the axial view of the counter gear 28, but this is not restrictive, and the guide ribs 60, 60 can be configured so as to overlap with at least either the driven gear portion 28 a or the input gear 26 of the motor output shaft 14 b in the axial view of the counter gear 28. For example, in FIG. 4, when the guide ribs 60, 60 are disposed closer to the imaginary line S, the guide ribs 60, 60 can overlap with both the driven gear portion 28 a and the input gear 26 in the axial view of the counter gear 28.

REFERENCE SIGNS LIST

-   14 Electric motor (Driving source) -   14 b Motor output shaft (Driving source output shaft) -   15 Transmission -   19 Gear train -   23 Case -   26 Input gear (Gear of driving source output shaft) -   28 Counter gear -   28 a Driven gear portion -   28 b Driving gear portion -   28 c Lower end (Part) -   34 Output gear (Lowermost-level gear) -   30 a Lower end -   32 Oil pan -   34 Other-side side wall (Side wall) -   34 b Inclined portion -   60, 60 Guide rib -   65 Lower end storage -   67 Lubricant guide surface -   67 c, 67 c Opposite ends -   67 d Central part 

1. A transmission comprising: a gear train driven by a driving source; a case that supports the gear train inside; lubricant with which the case is filled; and an oil pan provided at a bottom of the case, wherein the oil pan includes a lubricant guide surface positioned above a lower end of a lowermost-level gear that is positioned at the lowest position in the gear train, and the lubricant guide surface is inclined so as to descend toward the lowermost-level gear in an axial view of the lowermost-level gear, and is inclined so as to descend from opposite ends to a central part in the axial direction of the lowermost-level gear on the lubricant guide surface.
 2. The transmission according to claim 1, wherein the case includes a side wall facing a tip of a driving source output shaft of the driving source, and the side wall includes an inclined portion that is inclined so as to be more separated in the axial direction from the driving source output shaft toward the oil pan on a lower side.
 3. The transmission according to claim 2, wherein the gear train includes a counter gear that meshes with the driving source output shaft, and the lowermost-level gear that meshes with the counter gear, the counter gear integrally includes a driven gear portion that meshes with the driving source output shaft, and a driving gear portion that meshes with the lowermost-level gear, and at least a part of the driven gear portion is positioned inside the oil pan.
 4. The transmission according to claim 3, wherein a guide rib protruding to an inside of the case is formed in the inclined portion, and the guide rib extends in an up-down direction.
 5. The transmission according to claim 4, wherein the driving gear portion has a diameter smaller than that of the driven gear portion and is provided closer to the side wall side than the driven gear portion.
 6. The transmission according to claim 5, wherein the guide rib is provided above the driving gear portion, and overlaps with at least one of the driven gear portion and a gear of the driving source output shaft in the axial view of the counter gear.
 7. The transmission according to claim 1, wherein the oil pan includes a lower end storage that is depressed downward along the lower end of the lowermost-level gear to constitute a lower end of the oil pan.
 8. The transmission according to claim 7, wherein the lubricant guide surface is inclined so as to descend toward the lower end storage.
 9. The transmission according to claim 2, wherein the lubricant guide surface is provided below the inclined portion. 